YOU SAID:
time flys when you are having fun
INTO JAPANESE
楽しい時は時間があっという間に過ぎます
BACK INTO ENGLISH
Time flies when you're having fun
INTO JAPANESE
楽しんでいると時間はあっという間に過ぎます
BACK INTO ENGLISH
Time flies when you're having fun
That didn't even make that much sense in English.